68 lines
2.1 KiB
Go
68 lines
2.1 KiB
Go
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// Copyright 2022 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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// Package merkle implements proof verifications in binary merkle trees.
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package merkle
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import (
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"crypto/sha256"
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"errors"
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"reflect"
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"github.com/ethereum/go-ethereum/common"
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"github.com/ethereum/go-ethereum/common/hexutil"
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)
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// Value represents either a 32 byte leaf value or hash node in a binary merkle tree/partial proof.
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type Value [32]byte
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// Values represent a series of merkle tree leaves/nodes.
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type Values []Value
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var valueT = reflect.TypeOf(Value{})
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// UnmarshalJSON parses a merkle value in hex syntax.
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func (m *Value) UnmarshalJSON(input []byte) error {
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return hexutil.UnmarshalFixedJSON(valueT, input, m[:])
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}
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// VerifyProof verifies a Merkle proof branch for a single value in a
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// binary Merkle tree (index is a generalized tree index).
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func VerifyProof(root common.Hash, index uint64, branch Values, value Value) error {
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hasher := sha256.New()
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for _, sibling := range branch {
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hasher.Reset()
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if index&1 == 0 {
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hasher.Write(value[:])
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hasher.Write(sibling[:])
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} else {
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hasher.Write(sibling[:])
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hasher.Write(value[:])
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}
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hasher.Sum(value[:0])
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if index >>= 1; index == 0 {
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return errors.New("branch has extra items")
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}
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}
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if index != 1 {
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return errors.New("branch is missing items")
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}
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if common.Hash(value) != root {
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return errors.New("root mismatch")
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}
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return nil
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}
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